1. Field of the Invention
The invention pertains to vane-cell machines, and in particular, to vane-cell pumps.
2. Description of the Related Art
Conventional vane-cell machines are generally known, and comprise a rotor that rotates inside of a lifting ring that is arranged in a housing. The lifting ring has a contour that does not extend coaxially to the rotational axis of the rotor and forms at least one pump chamber. The rotor comprises radially extending slots, in which radially movable vanes are arranged. During the rotation of the rotor, the vanes are guided along the contour of the lifting ring, wherein respective chambers with changing volumes are formed between two adjacent vanes. In this case, a suction region and a pressure region are formed in accordance with the rotational movement of the rotor, wherein the suction region is arranged within the region of increasing volumes and the pressure region is arranged within the region of decreasing volumes. The suction region is connected to a suction connection of the vane-cell machine, and the pressure region is connected to a pressure connection of the vane-cell machine such that a fluid, e.g., oil, can be conveyed.
Machines known as lower vane pumps make up a lower vane pocket arranged within the suction region. The lower vane pocket is arranged in a lateral surface that limits the pump chamber. This lower vane pocket is connected to the pressure region of the vane-cell pump. The lower vane pocket is arranged in such a way that it is situated within the range of motion of lower vane chambers formed underneath the vanes in the slots in the rotor. In this case, the lower vane pocket extends over a certain rotational angle such that several lower vane chambers are simultaneously situated within the region of the lower vane pocket. Consequently, a fluid connection between the lower vane chambers and the lower vane pocket is attained, wherein the total surface of said fluid connection corresponds to the sum of the partial surfaces of the individual lower vane chambers that are currently in contact with the lower vane pocket.
The lower vane chambers change their cross-sectional surfaces in accordance with the rotational movement of the rotor and consequently change the radial position of the vanes, so the total surface also varies. The term "total surface" or "partial surface" of the fluid connection refers to the free cross-sectional surface of the fluid connection between the lower vane groove and the lower vane chambers situated within the region of a lower vane groove. The volume flow pulsation of the lower vane pump is superimposed on the volume flow pulsation of the upper vane pump and thus forms the total volume flow pulsation of the vane-cell pump.
In conventional vane-cell pumps, the lower vane pocket that is assigned to the suction region extends over a relatively large rotational angle of the rotor, i.e., the lower vane pressure pockets that are also situated within the range of motion of the lower vane chambers can only extend over a relatively small rotational angle. These lower vane pressure pockets are also connected to the lower vane pocket via the lower vane chambers and a circumferential groove in a second lateral surface, or four pockets are connected to one another via a fluid connection that is open toward the lower vane chambers.